Chain tension sensor

ABSTRACT

A chain tension sensor for a chain conveyor, the conveyor including a frame and a chain having a plurality of flights. The tension sensor includes a reaction arm and a load sensing pin. The reaction arm includes a first end, a second end opposite the first end, and a load pad. The first end is pivotably coupled to the frame by a pivot pin defining a pivot axis. The load pad is adjacent the conveyor chain and positioned to contact flights passing the load pad. The flights contacting the load pad exert a force on the reaction in a direction that is perpendicular to the pivot axis. The load sensing pin is coupled to the reaction arm such that the load sensing pin senses the force that is exerted by the flights.

RELATED APPLICATIONS

This application is a continuation-in-part of prior-filed, co-pendingU.S. application Ser. No. 12/767,411, filed Apr. 26, 2010, and alsoclaims the benefit of prior-filed, co-pending U.S. ProvisionalApplication No. 61/510,839, filed Jul. 22, 2011, and the entire contentsof both are hereby incorporated by reference.

FIELD

The present invention generally relates to mining equipment, and, inparticular, to drive chain conveyors. Still more particularly, thisapplication relates to a mechanism to sense the tension of a scraperchain of a chain conveyor.

BACKGROUND

Conveyors, such as armored face conveyors, are part of an integratedlongwall system that also comprises a coal-cutting machine and roofsupports. As the longwall system removes mineral from the mineral blockone strip (web) at a time, the load on the conveyor changes as thecutter moves along the conveyor. The conveyor progressively movesforward one web in order to reposition itself for the next cut.

The mineral being mined is dragged along a top race of the conveyor by acontinuous chain and flight bar assembly driven by sprockets at each endof the conveyor. More particularly, the conveyor typically includes apair of spaced apart chains with the flight bars connecting the chains.At the delivery end, the mineral is discharged onto an adjacent conveyorwhile the continuous chain enters a bottom race where it proceeds to areturn end, where a return end drum or sprocket reverses the directionof the chain.

Conventional longwall conveyors typically either operate at a fixedoverall length or may be fitted with a moveable end frame. The amount ofslack in the chain is controlled by applying a pre-tension to the chain.The pre-tension prevents chain extension, reducing the amount of slackgenerated.

An extendable end frame may be used to adjust the pre-tension by takingup increasing length of chain generated from inter-link wear and fromstretching in the chain that occurs due to the load on the chain. Thetension can be controlled by monitoring the amount of tension in thechain and adjusting the moveable end frame position with a feedback loopsystem.

The operation of the longwall system involves frequent repositioning ofthe many parts that make up the conveying system. Keeping the equipmentinline with the coal block is difficult, as no direct steering mechanismis available with these systems. The operators have to rely on theirexperience by adjusting the position of the conveyor relative to thecoal block to counteract a tendency of the equipment to gradually creepsideways. This results in face creep, and often the only correctiveaction available to the operators is to angle the conveyor a few degreesoff square to the coal block. This process is slow and requiresconsiderable skill. The variations in load and the repositioning of themany parts of the conveying system result in changes in chain tensions.

In certain operational situations, one of the chains of the chain andflight bar assembly may break on the top race. The unbroken chain canthen enter the return race along with the broken chain. Lower tensionsin the bottom race can be contained by the single chain, which continuesto the return end and then over the return end sprocket. If the brokenchain is not identified on the top race, the second chain will alsofail, most likely when the broken portion of the chain approaches adischarge area. This additional failure can cause damage to relatedequipment. The failure is followed by prolonged down time to make arepair. Visual identification of the broken chain is possible, but isunlikely because the chain is covered with the mineral being conveyed.Additionally, on most installations, safety requirements prohibitoperators from being adjacent the return end of the conveyor, whichfurther reduces the opportunity for manual detection.

FIG. 1, which is taken from Bandy U.S. Pat. No. 5,131,528, illustrates aprior art scraper chain conveyor. FIG. 1 illustrates in simple form thevarious conveyor elements necessary for understanding of the conveyorequipment environment. The conveyor apparatus or assembly is showngenerally by the character numeral 10 and includes a drive drum/sprocket12 and an idler or guide drum/sprocket 14 separated by a span of aflexible conveyor 16, illustrated partially in dashed line outline. Asdepicted, the conveyor 16 comprises dual conveyor chains 18 and amultiplicity of spaced flight bars 20 attached to the dual chains 18.During operation of the conveyor assembly, the flight bars 20 pushaggregate material, such as mined coal, along an underlying conveyor pan21. The conveyor assembly 10 is typically positioned juxtaposed to amine wall where a seam of material is being mined for transporting thematerial to one end. The material is then transferred to an auxiliaryconveyor for further disposition.

The drum/sprocket 12 is appropriately coupled to a conveyor drive motor22. Operation of motor 22 causes the sprocket intermeshing with the dualchains 18 to advance the conveyor 16. A pair of sidewalls 24 forming afirst portion of a “split frame” of conveyor assembly 10 serves torotatably support the drum/sprocket 12. The sidewalls 24 are illustratedas being telescopingly engaged with a second pair of sidewalls 26forming a second portion of the frame and, collectively with sidewalls24, comprise the aforementioned split frame. The telescoping joint,indicated generally by character numeral 48, permits the frame portionsto be moved relative to one another.

The idler drum/sprocket 14 is appropriately mounted for rotary movementbetween sidewalls 26. Relative movement at the joint 48 between theadjacent sidewalls 24 and 26 causes the distance between thedrum/sprockets 12 and 14 to vary accordingly. The dual conveyor chains18 can be provided with increased or reduced tension depending upon thedirection of adjusting movement of the supporting drum/sprockets withrespect to each other. To provide this relative movement, assembly 10has a tensioning means in the form of a pair of hydraulic cylinders 28,30. Each cylinder 28, 30 is mounted on and secured to an adjacentsidewall 26. In other embodiments (not shown), only a single hydrauliccylinder can be used. The cylinders 28, 30 include respective pistons32, 34, each of which is operatively coupled to a sidewall 24 in anyknown and expedient manner.

Movement of the pistons 32, 34 causes the first portion of the conveyor16 represented by the side walls 24 to move longitudinally relative tothe second portion and side walls 26, thus relaxing or tensioning thechain 18, as desired. Control of movement of pistons 32 and 34 isaffected by a conventional hydraulic tensioning control circuitry,depicted generally by numeral 40 in FIG. 1.

As stated above, a certain amount of tensioning of conveyor chain 18 isessential for the proper and efficient operation of the conveyorassembly 10. Too little tension may cause the conveyor chain to ride upthe teeth of the sprockets, and eventually become disengaged.Conversely, too much tension may cause the conveyor components to beover-stressed, increasing the risk of mechanical failure in the variousparts of the conveyor apparatus.

FIG. 2, which is taken from Weigel et al., U.S. Pat. No. 7,117,989,illustrates a prior art mechanism for controlling the tension in ascraper chain in a conveyor. FIG. 2 shows a tensionable return station51, which forms the auxiliary drive of a face conveyor and on which aspoked chain wheel 52 is located, which may be powered by drives (notshown).

All channel sections 70 and machine frame 51 and, where applicable, anyintermediate or transitional channels located between them, have a toprace 54A and a bottom race 54B. In the top race 54A the material to beconveyed (e.g. coal) is transported by means of scrapers 20 as far asthe main drive, and in bottom race 54B the scrapers run back to theauxiliary drive. The constantly changing load conditions in the top race54A cause the tension in the top race 54A and bottom race 54B ofconveyor 16 to vary.

In order to detect the tension of conveyor 16, a sensor, indicatedoverall by 60, is located on the frame of return station 51, which formsthe auxiliary drive. The sensor has a sliding body or sensor body 62with a curved sliding surface 61, which is coupled with a shaft 63 suchthat the sensor body 62 cannot be turned, said shaft reaching obliquelyover the conveying trough and return trough for scraper conveyor 16 intop race 54 A of machine frame 51 of the chain conveyor. Shaft 63 issupported in bearing blocks 64, one of which is indicated schematicallyat the rear side face of return station 51. The weight of sensor body 62causes its sliding surface 61 to be directly in contact with the upperface of a scraper 20 or with the upper face of vertical chain links 57in the area of the measuring zone. At the same time, shaft 63, supportedin bearing blocks 64 such that it can swivel, forms a measuring shaft,and by means of shaft encoder 65 the relative position of measuringshaft 63 and thus also the relative position or swiveled position ofsensor body 62 rigidly coupled with it may be detected and transmittedto the evaluation and control unit 72 via signal line 71. Depending onthe measurement signal of shaft encoder 65, evaluation and control unit72 then activates tensioning drive 55 of return station 51 via signalline 75.

In an extensive zone within top race 54A of return station 51, referredto below as the measurement zone, and extending between points 67 and 68in the drawing marked with double arrows, scraper conveyor 16 hasvertical play. In other words, between point 67 and point 68 along thetrack in top race 54A, conveyor 16 can essentially move freely in avertical direction, i.e. perpendicularly to the bottom of top race 73,74.

In the embodiment shown, the scraper chain is running with optimumtension, i.e. some chain links in the measuring zone are slightly liftedaway from the bottom of top race 74. When the chain is dangling, on theother hand, chain links 57, 58 and scrapers 59 within the area of themeasuring zone and in the area of the machine frame are in contact atevery point with the bottom of top race 73 or 74 of return station 51,and sensor body 62 is at its largest downwards deflection. This state isdetected by evaluation and control device 72 and tensioning drive 55 isextended. If the tension of scraper conveyor 16 increases, vertical andhorizontal chain links 57, 58 together with scrapers 59 of scraperconveyor 16 may move even higher in the measuring zone, due to theabsence of restrictive guidance and the existing vertical play (67 or68), which causes sensor body 62 to be swiveled clockwise and thisdeflection to be detected by shaft encoder 65 and transmitted toevaluation and control device 72 as a measurement signal. If the chainreaches a preset tension corresponding to that of a tight chain, this isdetected directly by shaft encoder 65 as a result of the greaterdeflection of sensor body 62, and evaluation and control device 72 thenactivates tensioning drive 55, in some cases via a closed-loop controlalgorithm, through signal line 75 such that tensioning cylinder 56 isretracted in order to reduce the tension in scraper conveyor 16.

Other mechanisms for monitoring chain tension include those shown inU.S. Pat. No. 5,505,293 and in U.S. Pat. No. 4,657,131.

In some existing constructions, load sensing pads are positioned in awear strip of a top flange in the moveable end frame. However, thispositioning exposes the pads to overheating resulting from friction.These load pads are also subjected to the full impact forces generatedfrom each flight member passing the load pad. In addition, in suchconstructions, the chain typically needs to be set at the highest loadto accurately measure the amount of slack generated as the chain is run,and setting the tension at the highest loading increases inter-linkwear, thereby reducing the life of the chain.

SUMMARY

This disclosure takes as its starting point the typical longwallconveyor described above in which the delivery end is fixed and thereturn end has a telescopic sliding frame. An object of this disclosuremay be to provide a device for detecting and adjusting the tension ofthe scraper chain, which determines the tension reliably and simply.Another object of this disclosure may be to provide such a device thatreliably senses chain tension while at the same time not adverselyaffecting the chain path.

This disclosure may also provide a means of identifying broken chain asit leaves the return sprocket and enters the top race of the conveyor.When detected, the chain can be stopped automatically by the armoredface conveyor control system, to avoid the potential for further damage,and warn the operators that repair of the chain is required.

Another object of this disclosure may be to provide sliding frames atboth ends of the conveyor to allow the conveyor ends to be independentlyadjusted to each end of the coal block, while maintaining good chaintension and control.

Providing the delivery and return end frames with a telescopic sectionaddresses the problem of face creep by allowing the operator to quicklyadjust the position of both ends of the conveyor, thus offsetting theeffects of face creep. This may be important on conventional enddischarge conveyor systems, where the correct relationship between thelongwall discharge conveyor and an auxiliary cross conveyor (beam stageloader) must be maintained. This problem presents an increasingchallenge where there are two longwall conveyors operating side by side,which is often the case with sub-level caving or longwall to coalcaving.

In one independent embodiment, a chain tension sensor is provided for achain conveyor, the chain conveyor including a frame and a chain havinga plurality of flights. The tension sensor may generally include areaction arm and a load sensing pin. The reaction arm may include afirst end pivotably coupled to the frame by a pivot pin defining a pivotaxis, a second end opposite the first end, and a load pad. The load padmay be adjacent the chain and positioned to contact the flights passingthe load pad. The flights contacting the load pad may exert a force onthe reaction arm in a direction perpendicular to the pivot axis. Theload sensing pin may be coupled to the reaction arm such that the loadsensing pin senses the force exerted by the flights.

In another independent embodiment, a chain conveyor may generallyinclude a conveyor frame, a chain having a plurality of flights, and atension sensor. The conveyor frame includes a first end and a secondend, the first end being moveable with respect to the second end. Thechain includes a plurality of flights and is supported by the frame suchthat the chain cycles between the first end and the second end.

The tension sensor includes a reaction arm, and a load sensing pin. Thereaction arm may be positioned proximate the first end of the conveyorframe and includes a hinge end pivotably coupled to the conveyor frameby a pivot pin defining a pivot axis, a sensor end opposite the hingeend, and a load pad adjacent the conveyor chain. The load pad may bepositioned to contact the flights as the flights travel between thefirst end and the second end of the conveyor frame, the flights exertinga force on the reaction arm in a direction that is perpendicular to thepivot axis. The load sensing pin may be coupled to the reaction arm suchthat the load sensing pin senses the force that is exerted by theflights.

In yet another embodiment, a sensor assembly is provided for detecting achain break in an endless conveyor, the conveyor including a frame, twospaced apart chains, and a plurality of flights connected between thechains. The sensor assembly may generally include a first sensordetecting a characteristic indicative of a tension of the one chain, anda second sensor detecting a characteristic indicative of a tension ofthe other chain, a difference between the tension of the one chain andthe tension of the other chain being evaluated.

In still another independent embodiment, a method is provided fordetecting chain tension in a conveyor chain, the chain being supportedby a conveyor frame and including a plurality of chain flights. Themethod may generally include providing a tension sensor including areaction arm having a first end pivotably coupled to the frame, a secondend opposite the first end and a load pad adjacent the chain, thetension sensor including a load sensing pin coupled to the frame and tothe second end of the reaction arm; contacting the load pad withflights; exerting a shear force on the load sensing pin; sensing theshear force exerted on the load sensing pin; and determining tension inthe chain.

Independent aspects of the invention will become apparent byconsideration of the detailed description, claims and accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a prior art delivery discharge end scraperchain conveyor arrangement.

FIG. 2 is a schematic view of a prior art tension sensor for detectingand tensioning a scraper chain.

FIG. 3 is a plan view of an improved tension sensor.

FIG. 4 is a perspective view of an alternate embodiment of the tensionsensor shown in FIG. 3.

FIG. 5 is a perspective view of the tension sensor shown in FIG. 4, asmounted at the return end of a conveyor.

FIG. 6 is a perspective view of a load cell used in the tension sensorof FIGS. 4 and 5.

FIG. 7 is a schematic top view of the chain, two tension sensors and atension control.

FIG. 8 is a top view of a conveyor and a secondary or auxiliaryconveyor.

FIG. 9 is a side view of the conveyor and auxiliary conveyor shown inFIG. 8.

FIG. 10 is a top view of a double conveyor system.

FIG. 11 is a perspective view of an end frame of a chain conveyor.

FIG. 12 is an enlarged view of the end frame of the chain conveyor ofFIG. 11.

FIG. 13 is a perspective view of a sensor assembly.

FIG. 14 is an assembly view of the sensor assembly shown in FIG. 13.

FIG. 15 is cross-sectional view of the sensor assembly shown in FIG. 13taken along line 15--15.

FIG. 16 is an enlarged cross-sectional view of the sensor assembly shownin FIG. 15.

FIG. 17 is an enlarged cross-sectional view of the sensor assembly shownin FIG. 15.

DETAILED DESCRIPTION

Before any independent embodiments of the invention are explained indetail, it is to be understood that the invention is not limited in itsapplication to the details of construction and the arrangement ofcomponents set forth in the following description or illustrated in thefollowing drawings. The invention is capable of other independentembodiments and of being practiced or of being carried out in variousways. Also, it is to be understood that the phraseology and terminologyused herein is for the purpose of description and should not be regardedas limiting. Use of “including” and “comprising” and variations thereofas used herein is meant to encompass the items listed thereafter andequivalents thereof as well as additional items. Use of “consisting of”and variations thereof as used herein is meant to encompass only theitems listed thereafter and equivalents thereof Further, it is to beunderstood that such terms as “forward”, “rearward”, “left”, “right”,“upward” and “downward”, etc., are words of convenience and are not tobe construed as limiting terms.

FIG. 3 illustrates an improved version of the tension sensing means 60shown in FIG. 2. Conventionally, to allow for optimum use of the lengthof the tailgate or return end or station 51, a wear strip 101 isinstalled to guide the conveyor 16 down to the track or race 54 A level.The tensioning means, or tension sensor 104, of FIG. 3, comprises a wearstrip 101 including a wear plate 108 that contacts the top surface ofthe conveyor 16.

The wear plate 108 is supported by a wear strip support 112, and thewear plate 108 is connected to the wear strip support 112 by a pin 116at one end and a load-sensing pin 120 at the other end. The wear plate108 engages the top surface of the conveyor 16, and changes the path ortrajectory of the movement of the conveyor 16. This contact and changein direction of the conveyor 16 causes a force to be applied on the wearplate 108. The load-sensing pin 120 that connects the wear plate 108 tothe wear strip support 112 senses this force. The output from theload-sensing pin 120 is then be used to determine the tension of theconveyor 16, and to adjust the tension, as needed, using anyconventional chain tensioning system, such as the joint 48 and pistons32 and 34 and circuitry of FIG. 1.

An alternate and preferred embodiment 124 of the tension sensor isillustrated in FIG. 4. In FIG. 4, a load cell 128 is located between awear plate 132 and a wear strip support 136. The load cell 128, which isillustrated in FIG. 6, is a cylinder including a plurality of spacedapart passageways 130 through the cylinder. Within the passageways areload sensors (not shown), which measure the compression force on theload cell 128. By placing the load cell 128 between the wear plate 132and the wear strip support 136, the load cell 128 responds to the forceapplied to the wear plate 132 by the conveyor 16. In order to provideredundancy, as shown in the preferred embodiment illustrated in FIG. 4,two spaced apart load cells 128 are placed between the wear plate 132and the wear strip support 136. More particularly, the wear stripsupport 136 includes a cavity 138 that receives the load cells 128, andthe wear plate 132 is connected to the wear strip support 136 by meansof a screw 140.

FIG. 5 illustrates a perspective view of the load sensor 124 mounted onthe conveyor apparatus 10 at the return end 51. As shown, the cavity 138receiving the load cells 128 can be formed by a plate 142 secured to thewear strip support 36. This provides ready access to the load cells 128from adjacent the conveyor apparatus 10, without the need forsignificant disassembly of conveyor parts. This thus permits readyaccess and repair of the tension sensor 124, when the need arises.

The disclosure also illustrates, in FIG. 7, the providing of two suchtension sensors on such a conveyor apparatus 10. More particularly, inthis embodiment, the conveyor 16 includes the two spaced apart chains18, and the plurality of flights or flight bars 20 that are connectedand spaced apart but between the two chains 18. Each conveyor flight 20has a first end and a second end. Each flight bar end is spaced apartfrom its respective adjacent chain. A tension sensor, such as thetension sensor illustrated in FIGS. 2, 3 and 4 above, is provided in arespective wear strip for each one of the two conveyor chains 18. Eachtension sensor 124 is electrically connected via a line 154 to acomparator 158.

In the preferred embodiment, as illustrated in FIG. 7, the part of theconveyor that contacts the tension sensor 124 is the end or tip of theflight bar 20. In other embodiments, not shown, a tension sensor 124 canbe placed above each of the chains, instead of the flight tips. The tipof the flight bar 20 will only contact the wear strip intermittently. Asa result, the tension sensor 124 will only produce intermittent signals.

To eliminate transient load spikes and to allow for the odd missingflight bar 20, the tension sensor 124 collects a rolling average readingover 20 or so flight bars. As each flight bar tip passes along the loadsensor, even at a constant chain tension, the signal varies due to thechanging geometry of the system. The tension sensor 124 records the peaksignal value as each flight bar 20 passes over the wear plate 132. Ifthe rolling average peak reading is too low, then the tension meansmoves the joint 48 to stretch the chain, or vice versa. The tensionmeans is initialized by establishing a required peak signal value bystopping the conveyor with a flight bar under the sensor, fitting atemporary load transducer to the chain itself, and then moving the joint48 to tension the static chain. When the chain is at the requiredtension, the tension sensor 124 stores the signal, and it is this signalvalue that the tension sensor 124 maintains while the conveyor isrunning

The above overview is a simplified version of the sensor signalmanagement system, and applies to steady chain load increase or decreaseduring the coal cutting cycle. The tension sensor 124 must also dealwith special events such as starting a full conveyor or the rapidunloading of a conveyor, like when the shearer stops cutting. Collectinga rolling average signal cannot respond quickly enough to deal withthese events, so advance action must be taken. For example, the sprocketis extended to significantly stretch the chain before loaded conveyorstartup to prevent generation of slack chain.

In the event of a chain break, the tension in the two chains 18 will bedifferent. The outputs of the tension sensors 124 are compared by acomparing means, comparator 158, and in the event of a significantdifference, the operation of the conveying apparatus 10 can be stoppedso the broken chain can be repaired. In the preferred embodiment, thetension sensors 124 are provided adjacent the top race of the return endof the conveyor apparatus. If additional sensors or sensing of thetension at other locations in the conveying apparatus is desired, othertension sensors 124, in other locations, can be used. The use of the twotension sensors 124 is also beneficial, for the output from the tensionsensors 124 can be averaged to produce a more accurate indication ofoverall conveyor tension. The comparator 158 forms a part of the chaintensioning system such as the joint 48 and pistons 32 and 34 andcircuitry of FIG. 1.

As illustrated in FIG. 8, an auxiliary or secondary conveyor 200 islocated at one end of a conveyor apparatus 210. The material on theconveyor 16 leaves the conveyor and is dumped onto the auxiliaryconveyor 200. During operation of the conveyor apparatus 210, thelocation of the conveyor apparatus 210 may move relative to the locationof the auxiliary conveyor 200. Currently, operators need to make variousadjustments in order to try to accommodate such movement. This canresult in difficulty maintaining conveyor operation.

In order to accommodate some movement of the conveyor apparatus 210relative to the auxiliary conveyor 200, the conveyor apparatus frameaccommodates sliding movement at both ends. At one end, the slidingmovement adjusts the tension of the conveyor 16, and sliding movement atthe other end accommodates movement of the conveyor apparatus 210relative to the auxiliary conveyor 200. If the conveyor apparatus 210moves relative to the auxiliary conveyor 200, an operator can move thesliding end of the conveyor 210 adjacent the auxiliary conveyor 200.Movement of the sliding end of the conveyor 210 can also be occasionedby the use of tensioning means, as described hereinafter, as used on thetensioning end 51 of the conveyor 16. Only in this instance, themovement is not intended to affect the tension of the conveyor 16, butthe location of the end of the conveyor apparatus 210 relative to theauxiliary conveyor 200. When movement at this end of the conveyoroccurs, the chain tension does change, so the other end of the conveyorapparatus 210 is adjusted by the automatic tensioning means to returnthe conveyor 16 back to the appropriate tension. Movement of the slidingend of the conveyor 210 adjacent the auxiliary conveyor 200 muchovercome the maximum working chain tensions (which are at there highestas these top chains reach this frame; plus significant sliding frictiondue to the typical large size and weight of the Main gate equipment.

More particularly, a driven drum/sprocket 312 is appropriately coupledto a conveyor drive motor 322. Operation of motor 322 causes thesprocket intermeshing with the dual chains 18 to advance the conveyor16. More particularly, as illustrated in FIGS. 8 and 11, in addition tothe hydraulic pistons 32 and 34 spanning the joint 48 at the return end51, a pair of sidewalls 324 forming a first portion of a “split frame”of the main gate end of the conveyor apparatus serves to rotatablysupport the drum/sprocket 312. The sidewalls 324 are illustrated asbeing telescopingly engaged with a second pair of sidewalls 326 forminga second portion of the frame and, which collectively with sidewalls324, comprise the aforementioned split frame. The telescoping joint,indicated generally by character numeral 348, permits the frame portionsto be moved relative to one another.

Relative movement at the joint 348 between the adjacent sidewalls 324and 326 thus causes the distance span between the drum/sprockets 312 and14 to vary accordingly. The conveyor 16 can be provided with increasedor reduced tension depending upon the direction of adjusting movement ofthe supporting drum/sprockets with respect to each other. To providethis relative movement, the conveyor assembly 310 has a pair ofhydraulic cylinders 328 and 330, each mounted on and secured to anadjacent sidewall 326. The cylinders have respective pistons 332 and334, each of which is operatively coupled to a sidewall 324 in any knownand expedient manner.

The location of the conveyor apparatus relative to the auxiliaryconveyor is further illustrated in FIG. 9. If desired, in lieu ofoperator correction of the location of the conveyor apparatus, theconveyor apparatus can be physically connected by a bar 352 to theauxiliary conveyor. In this instance, tension is maintained at this endof the conveyor by some tensioning means, such as the tensioning meanspreviously described. But in order to accommodate some movement in theevent the auxiliary conveyor and main conveyor change location, either ahydraulic accumulator (now shown), or some relief valve (now shown) mustbe provided in the hydraulic tensioning means in order to allow for themovement of this sliding end of the conveyor apparatus 210. When thisend of the conveyor apparatus 210 adjusts by movement of the auxiliaryconveyor 200, then tension is corrected, as described before, by thereturn end 51.

The problem of conveyor apparatus movement relative to the auxiliaryconveyor is especially relevant where a pair of conveyor apparatus isused. As illustrated in FIGS. 10A and 10B, it is known to use oneconveyor adjacent a coal face, and a second conveyor apparatus behindthe roof supports to collect coal that falls from the longwall roof asthe longwall advances. In this instance, the double sliding frame endswould be used with both conveyor apparatus.

Additionally the frame-sliding 48 and 348 can be adjusted to correctlyalign the conveyor end with both edges of the coal block, moving boththe return end frame and delivery end frame at the same time to maintaincorrect chain tension during this adjustment. This would not be a normalrequirement or mode of operation as the position of the Return End Frameto coal block is less critical in most cases.

This aspect of the disclosure thus has the following benefits. Manual orautomatic control of the delivery end frame sliding module makes fineadjustments for optimum discharge of material from the extendablelongwall armored face conveyor to the cross beam stage loader conveyor.

Since the changes in the overall length of the conveyor, as a result ofadjusting the delivery end sliding frame module will change the chaintension, adjustments must be in small increments and effected slowly togive the automatic chain tensioning system time to react. At all timesit is the automatic chain tensioning system that controls and maintainscorrect chain tension, not the adjustment of the delivery end framemodule.

In another embodiment, a sensor assembly 510 for detecting tension in achain 514 is provided. This embodiment is shown in FIGS. 11-17, and allreference numbers begin at 500.

FIGS. 11-12 illustrate a portion of a longwall conveyor 522 including areturn end 526 (FIG. 11), a conveying element or chain 530 that travelsbetween the return end 526 and a delivery end (not shown), and thesensor assembly 510 proximate the return end 526. The return end 526includes a frame 538, an idler or take-up shaft 542 mounted on the frame538, and at least one hydraulic actuator (not shown). The frame 538moves with respect to the delivery end, between an inner retractedposition and an outer extended position through the extension andretraction of the hydraulic actuator. The chain 514 passes around thetake-up shaft 542 to travel in a continuous loop between the deliveryend and the return end 526. The chain 514 includes a plurality of flightmembers 550 mounted on the chain 514 and spaced apart by a firstdistance in a direction of travel 554 of the chain 514.

As shown in FIGS. 13-16, the sensor assembly 510 is positioned adjacenta wear strip 562 of a flange portion 566 of the frame 538 and includes areaction arm 570, a main support hinge pin 574, a reaction bracket 578(FIGS. 14-16), a load sensing pin 582 (FIGS. 14-16), and a springassembly 586.

The reaction arm 570 has a first end 590, a shoulder 594, a second end598 (FIG. 14), and a load pad 602. The first end 590 is rotatablycoupled to a secondary support plate 606 of the frame 538 by the mainsupport hinge pin 574. The shoulder 594 is positioned proximate thefirst end 590. The second end 598 includes a hole 622 (FIGS. 14 and 15)extending from the second end 598 partially through the reaction arm 570in a longitudinal direction. The load pad 602 is positioned intermediatethe first end 590 and the second end 598. As shown in FIG. 12, the loadpad 602 is positioned parallel to the wear strip 562 to contact theflight members 550 passing the wear strip 562, causing the reaction arm570 to rotate about the hinge pin 574. The load pad 602 also provides acontinuous guide surface to guide the flight members 550 as the flightmembers 550 travel around the take-up shaft 542.

The hinge pin 574 is mounted to the secondary support plate 606 of theframe 538 and is positioned substantially transverse to the direction oftravel 554 of the chain 514. The hinge pin 574 restricts the motion ofthe reaction arm 570 in every direction except rotation (see arrow 630)about the hinge pin 574.

As shown in FIGS. 14-16, the reaction bracket 578 is mounted to thesecondary support plate 606 of the frame 538 and includes a slot 638.The reaction bracket 578 is configured to fit within the second end 598of the reaction arm 570 such that the slot 638 is aligned with the hole622 extending through the reaction arm 570. The load sensing pin 582 ispositioned in the slot 638 of the reaction bracket 578 and within thehole 622 of the reaction arm 570. The load sensing pin 582 is thereforepositioned substantially perpendicular to the hinge pin 574. The loadsensing pin 582 is attached to a sensing cable 650 (FIGS. 15 and 16).

As shown in FIG. 17, the shoulder 594 includes a head side 662, a springside 666, and a bore 670 extending between the head side 662 and thespring side 666 through the reaction arm 570 in a direction tangentialto a direction of rotation 630 of the reaction arm 570 (i.e.,perpendicular to the hinge pin 574). The spring assembly 586 includes abolt 670, a plurality of spring washers 674, and a retaining washer 678.The bolt 670 passes through the shoulder bore 670 from the head side 662to the spring side 666 and threadingly engages an internal thread (notshown) located on the wear strip 562 proximate the spring side 666.

The spring washers 674 are positioned around the bolt 670 adjacent thespring side 666, between the shoulder 594 and a cavity recess 686. Thecavity recess 686 reduces the material contact with the bolt 670,thereby reducing the amount of heat transfer from the wear strip 562 tothe bolt 670. The retaining washer 678 is positioned between the springside 666 of the shoulder 594 and the spring washers 674. Each springwasher 674 has a generally frusto-conical shape that creates a springforce as the spring washer 674 is compressed. The retaining washer 678centers the top-most spring washers 674 with respect to the bolt 670.

As the bolt 670 is tightened, the retaining washer 678 compresses eachspring washer 674, and the reaction arm shoulder 594 is secured againstthe retaining washer 678. Tightening the bolt 670 causes the retainingwasher 678 to draw closer to a bolt shoulder 686. Once the retainingwasher 678 contacts the bolt shoulder 686, the bolt 670 cannot betightened any further. In this way, the bolt shoulder 686 providesmechanical lock-out by preventing over-compression of the spring washers674. The compression of the spring washers 674 applies a spring force tothe reaction arm 570, biasing the reaction arm 570 away from the frame50. The spring washers 674 may be stacked in a number of configurationsin order to obtain the desired pre-load force on the reaction arm 570.Alternatively, a single spring washer 674 may be used. In otherconstructions, a different type or shape of spring may be used. Inanother alternative, a plurality of shims may be added to the areabetween the retaining washer 678 and the cavity recess 686 in order toaccount for the build-up of tolerances in the bolted joint and also toapply additional compressive force on the spring washer(s) 674.

During operation, the load pad 602 of the reaction arm 570 contacts theflight members 550 of the chain 514 as the flight members 550 passbetween the return end 50 and the delivery end. In this manner, the loadpad 602 is subjected to the vertical component of the chain tension.Contact with the flight members 550 causes the reaction arm 570 torotate about the hinge pin 574. Referring to FIG. 5, as the reaction arm570 rotates, the second end 598 deflects upwardly, exerting an upwardforce on the load sensing pin 582. The reaction bracket 578 resists thisdeflection, exerting a downward force on the load sensing pin 582. Theload sensing pin 582 senses the magnitude of the shear force andtransmits a signal indicative of the force through the sensing cable 650to a chain controller (not shown). The chain controller then uses thisinformation to determine the tension in the chain 514 and to calculatethe necessary change in position of the return end frame 50 in order tomaintain the desired tension in the chain 514. The chain controller maybe a component of a system, for automatically controlling the conveyor10, such as that described and illustrated in U.S. Provisional PatentApplication No. 61/510,850, filed Jul. 22, 2011, the entire contents ofwhich are included in parent U.S. Provisional Application No. 61/510,839and are also hereby incorporated by reference.

The biasing force of the spring assembly 586 provides a pre-load forcethat can be calibrated. Instead of calibrating the tension to themaximum load the chain 514 may experience during operation (which may beas high as 5 tons), the positive pre-load permits the chain tension tobe set to a lesser load. This may reduce inter-link chain wear andsprocket wear and, ultimately, increase the life of the chain 514. Inone example, a pre-load in the range of 200 to 400 lbs. may provideimproved results for even very high material loads. Also, the positivebase load may facilitate accurate measurement in strain gauge sensors,enhancing accuracy of the system. In addition, the positive pre-load mayalso reduce the occurrence of negative outputs, which can falselytrigger system alerts.

Due to the perpendicular orientation of the load sensing pin 582 withrespect to the hinge pin 574, the load sensing pin 582 only senses thevertical component (e.g., the rotation of the reaction arm 570 about thehinge pin 574) of the force exerted on the reaction arm 570. Thiseffectively isolates the load sensing pin 582 from impacts to the loadpad 602 of the reaction arm 100, resulting in improved reliability and amore accurate electrical signal. Also, in one embodiment, the load pad602 has a length that is a significant proportion of the distancebetween the flight members 550. In one embodiment, the load pad 602 hasa length in a range between approximately 60% and approximately 70% ofthe distance between the flight members 550. This significant lengthprovides a smaller gap between the moment when one flight member 550contacts the load pad 602 and the moment when a second flight member 550contacts the load pad 602, reducing the oscillation of the load pad 602(and therefore the load sensing pin 582) between a loaded position andan unloaded position. This aids the load sensing pin 582 in generating asmooth, level signal. Spurious loading arising from the impact of theflight members 550 with the load pad 602 is absorbed by the main supporthinge pin 574, which is positioned at a right angle to both thedirection of travel 80 of the chain 514 and the flight members 550. Inaddition, the load sensing pin 582 is not directly in contact with thewear strip 562, reducing the impact loading and insulating the loadsensing pin 582 from heat caused by the friction contact of the flightmembers 550 sliding against the underside of the wear strip 562.

In an alternative independent embodiment, the conveyor 514 may include aplurality of load sensor assemblies 510. For example, the conveyor 514may include a sensor assembly 510 mounted on each side of the chain 514,allowing the sensor 510 to measure the tension in each chain 514independently and permitting the operator to detect breakage in eitherchain 514. Since the chains 514 are connected to one another by theflight members 550, some amount of the tension load in the chains 514will be shared in the event that a chain 514 breaks. In addition, whilethe described location of the sensor assembly 510 is beneficial becausethe sensor assembly 510 is subjected to less direct impact loads, in analternative embodiment the sensor assemblies 510 may be spaced along thelength of and on either side of the conveyor 514.

Thus, the invention may generally provide, among other things, a chaintension sensor.

1. A chain tension sensor for a chain conveyor, the conveyor including aframe and a chain having a plurality of flights, the tension sensorcomprising: a reaction arm including a first end pivotably coupled tothe frame, a second end opposite the first end, and a load padpositioned adjacent the conveyor chain, flights contacting the load padexerting a force on the reaction arm; and a load sensing pin coupled tothe reaction arm and operable to sense the force exerted by the flights.2. The tension sensor of claim 1, wherein the chain travels in a firstdirection, and wherein the reaction arm is pivotably coupled to theframe by a pivot pin defining a pivot axis, the pivot axis beingperpendicular to the first direction.
 3. The tension sensor of claim 2,wherein the load sensing pin defines a pin axis, the pin axis beingsubstantially parallel to the first direction.
 4. The tension sensor ofclaim 1, wherein the load sensing pin is coupled to the second end ofthe reaction arm.
 5. The tension sensor of claim 4, wherein the secondend of the reaction arm defines an opening, and wherein a portion of theload sensing pin is received in the opening.
 6. The tension sensor ofclaim 1, wherein the force exerted by the flights on the reaction armplaces the load sensing pin in shear, and wherein tension in the chainis determined based on a sensed shear force.
 7. The tension sensor ofclaim 1, further comprising a spring assembly coupled between thereaction arm and the frame.
 8. The tension sensor of claim 7, whereinthe spring assembly exerts a pre-load force on the reaction arm in adirection opposite the force exerted by flights contacting the load pad.9. The tension sensor of claim 7, wherein the spring assembly includes abolt connected between the reaction arm and the frame, and a pluralityof spring washers positioned on the bolt and between the reaction armand the frame.
 10. The tension sensor of claim 1, wherein the reactionarm has an arm length, and wherein the load pad has a load pad lengththat is approximately 60% to 70% of the arm length.
 11. A chain conveyorcomprising: a conveyor frame including a first end and a second end, thefirst end being moveable with respect to the second end; a chain havinga plurality of flights, the chain being supported by and movable on theframe to cycle between the first end and the second end, movement of thefirst end of the frame relative to the second end of the frame adjustinga tension in the chain; a reaction arm positioned proximate the firstend of the frame, the reaction arm including a hinge end pivotablycoupled to the frame, a sensor end opposite the hinge end, and a loadpad positioned adjacent the chain, flights contacting the load padexerting a force on the reaction arm; and a load sensing pin coupled tothe reaction arm and operable to sense the force exerted by the flights.12. The chain conveyor of claim 11, wherein the reaction arm ispivotably coupled to the frame by a pivot pin defining a pivot axis, thepivot axis being perpendicular to a direction of travel of the chain.13. The chain conveyor of claim 11, wherein the load sensing pin definesa pin axis, the pin axis being substantially parallel to a direction oftravel of the chain.
 14. The chain conveyor of claim 11, wherein theload sensing pin is coupled to the frame and to the second end of thereaction arm.
 15. The chain conveyor of claim 14, wherein the second endof the reaction arm is positioned adjacent a bracket connected to theframe, and wherein the load sensing pin extends through the bracket andis coupled to the reaction arm.
 16. The chain conveyor of claim 15,wherein the second end of the reaction arm defines an opening, andwherein a portion of the load sensing pin is received in the opening.17. The chain conveyor of claim 11, wherein the force exerted by theflights on the reaction arm places the load sensing pin in shear, andwherein tension in the chain is determined based on a sensed shearforce.
 18. The chain conveyor of claim 11, further comprising a springassembly coupled between the reaction arm and the frame, the springassembly exerting a pre-load force on the reaction arm in a directionopposite the force exerted by the flights.
 19. The chain conveyor ofclaim 11, further comprising an actuator for moving the first end of theframe relative to the second end of the frame to adjust the tension inthe chain.
 20. A sensor assembly for sensing a chain break in an endlessconveyor, the conveyor including a frame, two spaced apart chains, and aplurality of flights connected between the chains, the sensor assemblycomprising: a first sensor sensing a characteristic indicative of atension of the one chain; and a second sensor sensing a characteristicindicative of a tension of the other chain, a difference between thetension of the one chain and the tension of the other chain beingevaluated.
 21. The sensor assembly of claim 20, wherein the first sensoris coupled to the frame and positioned adjacent to the one chain, andwherein the second sensor is coupled to the frame and positionedadjacent the other chain.
 22. The sensor assembly of claim 21, whereinthe chains move along an axis, and wherein the first sensor and thesecond sensor are positioned on the frame generally on a lineperpendicular the axis.
 23. The sensor assembly of claim 21, wherein thechains move along an axis, and wherein the first sensor and the secondsensor are positioned on the frame spaced apart along the axis.
 24. Thesensor assembly of claim 20, further comprising a comparator fordetermining the difference in the tension of the one chain and thetension of the other chain.
 25. The sensor assembly of claim 20, whereinthe first sensor includes a load cell positioned between the one chainand the frame, the load cell measuring a force exerted by the flights.26. The sensor assembly of claim 25, wherein the second sensor includesa second load cell positioned between the other chain and the frame, thesecond load cell measuring a force exerted by the flights.
 27. Thesensor assembly of claim 20, wherein the first sensor includes areaction arm including a first end pivotably coupled to the frame by apivot pin defining a pivot axis, a second end opposite the first end,and a load pad positioned adjacent the other chain, flights contactingthe load pad exerting a force on the reaction arm, and a load sensingpin coupled to the reaction arm and operable to sense the force exertedby the flights.
 28. The sensor assembly of claim 27, wherein the secondsensor includes a second reaction arm including a first end pivotablycoupled to the frame by a second pivot pin defining a second pivot axis,a second end opposite the first end, and a second load pad positionedadjacent the other chain, flights contacting the second load padexerting a force on the second reaction arm, and a second load sensingpin coupled to the second reaction arm and operable to sense the forceexerted by the flights.
 29. A method for sensing chain tension in aconveyor chain, the chain being supported by a conveyor frame andincluding a plurality of chain flights, the method comprising: providinga tension sensor including a reaction arm having a first end pivotablycoupled to the frame, a second end opposite the first end and a load padadjacent the chain, the tension sensor including a load sensing pincoupled to the frame and to the second end of the reaction arm;contacting the load pad with flights; exerting a shear force on the loadsensing pin; sensing the shear force exerted on the load sensing pin;and determining tension in the chain.